Bandwidth monopole antenna having low ground losses due to a circumferential ground ring



May 24, 1966 R. L TANNER 3,253,279

BANDWIDTH MONOPOLE ANTENNA HAVING LOW GROUND LOSSES DUE TO ACIRCUMFERENTIAL GROUND RING Filed Feb. 1, 1965 4 Sheets-Sheet 1 2055/27L. T4 MvE/e INVENTOR.

d8 BY/M PRIOR ART A TTORNE) May 24, 1966 R. L TANNER BANDWIDTH MONOPOLEANTENNA HAVING LOW GROUND LOSSES DU Filed FEb. 1, 1963 4 Sheets-Sheet 2iii INVENTOR [9055/2 L. TA NNE Q A 7TORNEY May 24, 1966 R. 1.. TANNERBANDWIDTH MONOPOLE ANTENNA HAVING LOW GROUND LOSSES DUE TO ACIRCUMFERENTIAL GROUND RING 4 Sheets-Sheet 5 Filed Feb. 1, 1963 ROBERT A774 lV/VER A 77'OR/ EV United States Patent Ofi Frce 3,253,279 PatentedMay 24, 1966 BANDWIDTH MONUPULE ANTENNA HAVING LUW GROUND LUSSES DUE TOA CIRCUMFER- ENTIAL GROUND RING Robert L. Tanner, Menlo Park, Calif,assiguor to TRG, Incorporated, Palo Alto, Calif., a corporation of NewYork Filed Feb. 1, 1963, Ser. No. 255,439 12 Claims. (Cl. 343849) Thisinvention relates to antennas of the monopole type which are used forlow frequencies and very low frequencies and more particularly toimprovements there- This application is a continuation-in-part ofapplication Serial No. 225,815, and now abandoned, for a MonopoleAntenna by this inventor.

Radio waves at frequencies below 300 kc. are used for a number ofspecialized applications. They form the basis of long range radionavigation systems and long range communications systems because of thefact that they suffer relatively low propagation attenuation and areless affected by changes in ionospheric conditions than are waves orhigher frequency. In addition, waves at very low frequencies (VLF)-inthe vicinity of kc.have the useful property that they penetrate seawater to significant depths and are therefore useful for communicationwith submerged submarines.

A principal difficulty in the use of frequencies below 300 kc. is theexpense of the antenna and ground systern required to reduce groundlosses to acceptable values. Because the wave length is so large theantenna, even though it may be a very high tower, is still electricallysmall so that the radiation resistance is very low. The effective heightis approximately /2 of the actual height if the antenna is a simpletower. If the antenna is top loaded the effective height may approachthe actual height.

As an example, consider an antenna for operation at 15 kc. Assume theantenna to have an effective height of 200 meters which would require atower 700 to 1000 feet high with substantial top loading. At thisfrequency the wave length equals kilometers (20,000 meters). It can beshown that for this wavelength an antenna having an effective height of200 meters has a radiation resistance equal approximately to 0.16.Because the radiation resistance is so low, such an antenna can beobtained only if the loss resistance due to ground losses is reduced toa very low value. At the present time this is accomplished by i-mbeddingin the ground a great number of copper ground wires which extend fromthe base of the antenna tower to a substantial distance from it. As aconsequence, antennas for operating at this frequency range are verycostly.

It is an object of the present invention to provide a novel monopoletype antenna which effectuates a great reduction in cost while achievinga given efficiency.

Another object of the present invention is to provide a novel monopoleantenna which has a substantially improved bandwidth characteristicwithout increasing the cost of said antenna.

Another object of the present invention is the provision of a novelstructure for a monopole antenna.

Yet another object of the present invention is the provision of amonopole antenna having a unique structure whereby most of the groundlosses and much of the cost of the installation of a ground system iseliminated.

These and other objects of the present invention may be achieved in anantenna arrangement utilizing a single tower supported by guy wires.Attached to the top of the tower are a plurality of radiating lines.Both guy wires and radiating lines are coupled to a large ring conductorso that the antenna effectively describes the shape of a circular cone.The ring is in contact with the earth. It may be either buried, laid outover the surface of the earth, or supported a very small distance abovethe surface. By installation of the ring and associated conductors inthe manner to be described, the necessity for installation in the groundof wires radiating from the base of the tower to reduce ground losses iseliminated. Ground current density is considerably reduced by thisarrangement, and ground losses minimized. In addition, the guy wiresassociated with the antenna support tower are connected in a manner tooperate as large inductors which are excited and connected to theradiating wires to help resonate or tune the antenna, and to provideadditional radiation from a loop radiation mode which augments theradiation from the normal electric dipole radiation mode of the antenna.

The novel features that are considered characteristic of this inventionare set forth with particularly in the appended claims. The inventionitself, both as to its organization and method of operation, as well asadditional objects and advantages thereof, will best be understood fromthe following description when read in connection with the accompanyingdrawings, in which:

FIGURE 1 is a schematic drawing of a conventional top loaded monopoleantenna;

FIGURE 2 is a diagram showing distribution of ground current at the baseof a conventional monopole antenna;

FIGURE 3 is a diagram showing distribution of current at the base of anantenna built in accordance with this invention;

FIGURE 4 is an antenna built in accordance with the teachings of thisinvention;

FIGURE 5 is a diagram showing the manner in which the supporting towerguy wires are utilized in accordance with the teachings of theinvention;

FIGURE 6 is similar to FIGURE 5 but shows the guy wires interconnectedin a manner to permit operation at lower frequencies;

FIGURE 7 is a view of a portion of the antenna showing the arrangementof the ground current distribution bus and the current equalizingreactors;

FIGURE 8 is a diagram showing a tapered wave guide which is useful inexplaining the improved broadband properties in antennas built inaccordance with this invention;

FIGURE 9 is a view of another arrangement for ground currentdistribution in accordance with this invention.

Reference is now made to FIGURE 1 wherein there is shown a schematicdrawing of a conventional toploaded or umbrella antenna commonlyemployed for radiating LP or VLF signals. The antenna comprises a tower10 which is connected to a transmitter 12. Top loading conductors 14 areconnected to the top of the tower. The purpose of these conductors is toincrease the effective height and capacitance of the antenna. Radiatingout from the base of the antenna and also connected to the groundterminal of the transmitter 12, are radial ground conductors 16.

Current enters the ground system at the center of the radial groundconnectors 16. Although most of the current flows in these conductors, asignificant portion is carried in the ground itself, and this portionincreases as the wave travels out from the base of the tower. Beyond theends of the ground conductors all current is carried in the ground.

FIGURE 2 represents with arrows 18, the radial currents which flow atthe base of a conventional monopole antenna such as is represented inFIGURE 1. FIGURE 2 is an approximately quantitative representationinasmuch as the spatial density (number per unit of transverse length)of the arrows is a measure of the ground current density.

FIGURE 3 represents the ground currents which flow at the base of anantenna which is constructed in accordance with this invention. Thelarge circle represents a ground conductor ring 20 which, as will beshown subsequently herein, is a part of the antenna system of thisinvention. The arrows 22, represent the near-zone ground current. Thetotal current in the two cases is approximately the same, but it isevident that the current density in FIGURE 3 is many times smaller. Thisresults in part from the fact that the current entering the ground onthe large diameter ring 20 is spread over a much greater circumferentialdistance. In addition, the near-zone base current in FIGURE 3 divideswith part flowing toward the center and part flowing away from thecenter, while in FIGURE 2 the current is constrained by the geometry toflow outward exclusively. This results in an additional reduction incurrent concentration. In fact, it can be shown that if the beneficialeffect of ground radial conductors is not present the ground lossresistance, in the case represented by FIGURE 2, may be more than 100times as great as in the case represented by FIGURE 3. Thus, arudimentary ground system consisting of a ground conductor ring 20,which may be a single wire as shown, or two or more spaced wires, giveslower ground losses than even an expensive and elaborate ground radiosystem for a conventional antenna.

Reference is now made to FIGURE 4 which is a drawing of an embodiment ofthis invention. A support tower 24 is held insulated from the ground byan insulating support 26. The support tower is held in place byconventional guy system consisting of outer guys respectively 30A, 32A,34A, 30B, 32B, 34B, 30C, 32C, 34C, and inner guys respectively 36A, 38A,40A, 36B, 38B, 40B, and a third set of inner guys, which are not shown.Typically there are 3 groups of guys spaced around the tower atintervals of 120. Typically also, the guys are insulated from the towerand from the guy anchors by strain insulators. In the embodiment of theinvention, guy wires 32A through 32C, 34A through 34C, 36A through 36C,38A through 38C, 40A through 40C, are anchored in this fashion namely byusing strain insulators 44 which insulate the guys from the tower andfrom the guy anchors.

At this point it should be noted that another feature of this inventionis a ground distribution bus ring 46 which circles the base of theantenna. Typically, this ground distribution bus ring is installed at adistance above the ground which is high enough to provide adequateground clearance for personnel and equipment but low enough to be easilyaccessible for maintenance. The bus ring 46 may be a single conductor asshown but preferably is made of parallel multiple spaced conductors toreduce its inductance and increase its capacitance to ground as well asto reduce resistive losses. The bus ring may be supported directly fromradiator support cables 52, to which it is connected, or it may besupported from a ring of auxiliary support poles.

At the top of the tower there is shown a radiator support insulator 48.This insulator has the purpose of providing mechanical support forradiator wires 50 and upper guy wires 30A, 30B, and 30C, whileelectrically insulating them from the tower. All of the wires supportedby the insulator are attached to a common con nection 49 at the top ofthe insulator, and are thus conductively connected together at thatpoint. The radiator wires 50 are anchored to the ground by means ofsupport cables -2. These support cables are insulated from the radiatorwires 50 by strain insulators 44. The lower end of each one of the guywires 30A, 30B, 300, is mechanically connected to ground through astrain insulator 44 the other side of which is connected to the grounddistribution bus ring 46 and also to current equalizer reactor 54.Similarly, each one of the radiator support cables 52 is connected tothe ground distribution bus ring 46 and then to ground through a currentequalizer reactor 54. It should be noted that ground connection is madeto the ground conductor ring 20, which is buried in the ground at adistance which should not exceed a fraction of the skin depth at thefrequency of excitation of the antenna. Preferably, the depth should beon the order of 0.2 the skin depth. In order to improve the performanceof the ground conductor ring in reducing the ground losses by reducingthe current density in the ground, additional short radial conductors 56may be evenly spaced around the ground conductor ring 20, and areconnected thereto at their centers. These short radial conductors arealso positioned at each location at which a connection is made to theground conductor ring by either one of the current equalizinginductances 54 or by the anchors for the guy wires. Connections betweenthe ground distribution bus ring 46 and the ground conductor ring 20should be made at intervals of two or three times the skin depth, andeach connection should employ a current equalizing reactor of the propervalue.

One terminal of the transmitter 58 is connected to the grounddistribution bus ring 46, and the other terminal is connected to the guywire 32A. A conductive connection is made between the guy wire 30A viaconductor 60A to the guy wire A. Guy wire 40A is connected to the upperend of guy wire 32A by a conductor 62A. Effectively a one and one halfturn inductance has been formed between connection point 49 and thetransmitter 58 made up of guy wire 30A conductor 60A, guy wire 40A,conductor 62A guy wire 32A. The remaining guy wire sets areinterconnected in a similar manner by conductors for forming inductorsbetween connection point 49 and the ground current distribution bus 46.In this connection the respective guy wires 32B and 32C are connected tothe ring 46 by conductors 65A, 65B. Conductors 62A, 62B are respectivelyemployed for connecting guy wire 40A to guy wire 32A, guy wire 40B toguy wire 32B. Not shown is a conductor for connecting guy wire 40C toguy wire 42C. FIGURE 5 is an elevation view of FIGURE 4 showing only theguy wires just described. For further simplifying FIGURE 5 theconnections of the various guy wires on the ground side of the straininsulators 44 are all shown as being made directly to ground. Only twosets of guy wires are shown, the third set is similar in configurationto those shown.

Consider now FIGURE 4 together with FIGURE 5. It will be noted that theradiator wires are excited from the common connection with the guy wire30A at point 49. At one instant in the radio frequency cycle ofoperation, charge which is stored on radiator wires 50 is a maximum. Theantenna voltage is maximum and current flow in the antenna system iszero. As time goes on the charge stored on the antenna starts to flowofif resulting in a current flow in the conducting paths to ground.FIGURE 5 shows two of the existing three paths along which currentsrepresented by the arrows 64, 64A, must flow. Tracing through thesepaths, it is seen that each one consists of a large one-and-one-halfturn loop inductor consisting of upper guy wire 30A, 30B respectively inseries with conductive jumpers A, 60B respectively in series with lowerguy wires 40A, 40B, respectively in series with conductive jumpers 62A,62B, respectively in series with upper guy wires 32A, 32B, and in thecase of guy wire 32B a connection is made through the jumper 65A to theground distribution bus ring 46 and therefrom to ground. The guy wire32A is connected to the transmitter 58.

The large inductances so formed tune the antenna to operate at arelatively low frequency. Typically such an arrangement can be designedto tune a 600-foot antenna to a frequency of between 50 and 60kilocycles. The tuning inductor achieved in this way has severaldistinct advantages. It utilizes necessary structure to achieve a tuningsystem of high efiiciency and virtually unlimited power rating. Inaddition, the arrangement described contributes to the radiation fromthe antenna. The inductors composed as described from the guy wires formloop antennas having large enough areas to have appreciable radiationresistance. Furthermore, it will be evident to those well skilled in theart that the three loops so formed, having their planes vertical butspaced in azimuth by 120 provide a composite radiation pattern identicalto the electric dipole radiation pattern of the antenna. Radiation fromthe loops therefore augment the radiation from the dipole mode, therebyincreasing both the efiiciency and the bandwidth of the antenna.

In FIGURE 4 the tower 24 is shown as being insulated from ground by abase insulator 26. In addition radiators 50 are connected to each otherat the top but are shown insulated from the tower by support insulator48. This is a preferred construction and yields the highest performance.It is possible however, to eliminate one or the other of the insulatorsin the interest of convenience and economy. For example, by eliminatinginsulator 26 the tower is grounded. This permits access to the tower bypersonnel even when the antenna is in operation. It simplifiesinstallation of obstruction lights, eliminates need for a lightningarrestor gap at the base and provides lightning protection to theantenna system as a whole by enabling a grounded lightning rod to beinstalled so as to project substantially higher than any other part ofthe structure. In addition, the grounded tower arrangement enables thetower to be used for the installation of other antennas and equipmentsuch as microwave or UHF relay equipment without in any way interferingwith the opera tion of either the LP or of the additional equipment.

Grounding the tower by elimination of insulator 26 reduces theperformance of the antenna somewhat however. The principal effect is areduction of approximately in the available bandwidth, although groundlosses are increased slightly also.

Alternatively, radiators 50 can be connected directly to the tower,eliminating insulator 48. This also reduces the performance of theantenna, but not as much as grounding the tower. In this case, however,there are not the compensating advantages of the grounded tower.

Each one of the current equalizer reactors 54 which separate the lowerends of the radial support cables 52 from ground are shown on thedrawing as being inductors. They may also be capacitors, provided thevalues of the capacitors are properly chosen. If the operation of theantenna is limited to a relatively narrow frequency range, thecapacitors are preferred. If the antenna is to operate over a very broadfrequency range, there are some advantages to the use of inductors. Oneconvenient way to achieve these inductors is to slip high permeabilityferrite sleeves over the lower end of the cables 52. Alternatively, thecables can be broken by low voltage strain insulators and a separateequalizing reactor can be connected across each one of the insulators.

Reference is now made to FIGURE 6 which is similar to FIGURE 5 exceptthat it shows an arrangement of interconnecting conductors between theguy wires in a manner to form, together with the guy wires, inductorshaving two and one-half turns. Such an arrangement permits operation atstill lower frequencies with the same beneficial effect. It will be seenthat there is a conductor 66A which connects the lower end of guy wire30A to the lower end of guy wire 38A. A conductor 66B connects the lowerend of guy wire 30B to the lower end of guy wire 38B. A conductor 68Aconnects the lower end of guy wire 32A to the lower end of guy wire 40A.A conductor 68B connects the lower end of guy wire 32B to the lower endof guy wire 403. A conductor 70A connects the upper end of guy wire 40Ato the upper end of guy Wire 34A. A conductor 70B connects the upper endof guy wire 40B to the upper end of guy wire 34B. A conductor 72Aconnects the upper end of guy wire 38A to the upper end of guy wire 32Aand a conductor 72B connects the upper end of guy wire 38B to the upperend of guy wire 32B. The two and a half turn loop inductors should bereadily visible in FIGURE 6. The third set of upper and lower guy wiressets, not shown, are similarly interconnected.

In addition to the inductance provided by interconnected guy wires,additional inductance can be added in series with the connections 65,65A, 658, which are used to connect the respective guy wires 32B, 32C,to the bus, ring conductor. Also additional inductance can be added inseries with the transmitter 58. Normally, it is sufiicient to addinductance in series with just one of these, most conveniently thetransmitter, to achieve a desired measure of fine tuning control. Italso is evident that if operation at higher frequencies is desired thegrounding connectors 65A, 65B, and the transmitter 58 can be connecteddi rectly in series with upper guy wires respectively 30A, 30B, 30C, toachieve one-half turn inductors with lower inductance. Still lowerinductance can be achieved by disconnecting jumpers 66, 68, 70, 72, andconnecting guy wires 30, 32, 34, in parallel by suitable interconnectingjumpers at their upper and lower ends.

In FIGURE 7 there is seen a view of a portion of the antenna showing onemajor segment 46A. of the ground distribution bus ring 46 and theassociated structures. Currents represented by dashed arrows 64 and 64Aenter the ground distribution bus ring 46 at connection pointsrespectively 74 and 76. At point 74, slightly less than half of thecurrent flows to the left as current 64L, and an equal amount flows tothe right as current 64R. A smaller amount of current 64G flows into theground conductor 20 and thence into the ground. Part of the current 64Rflows into the ground through the next succeeding current equalizinginductance 54 as current 64G thus the remaining current 64R flows on thebus ring to the succeeding connection of the next current equalizinginductance where still more current can flow into the ground. Theremaining current continues on and some of it flows into the ground atthe next equalizing inductance. Thus, the manner of current flow aroundthe ring and into the ground through the equalizing inductances is seen.

By proper choice of the values of the reactive elements 54 or equalizinginductances, the currents flowing through these reactive elements can beequalized. As pointed out previously, the best performance may beobtained at a given frequency by the use of capacitors for elements 54rather than the inductors which are shown. The values of thesecapacitors can be equal and should be chosen in conjunction with theinductance of the ground distribution bus ring 46 so as to make thelength of the conductor 46 between connection points '74, 76,approximate a lumped-loaded transmission line of one-half wavelengtheffective electrical length. As mentioned previously, connectionsbetween bus ring 46 and ground conductor 20 should be on the .order oftwo or three times the skin depth preferably, but may be as great asfour times the skin depth in the earth without seriously impairing theoperation of the antenna.

Reference is now made to FIGURE 8 where there is shown a section of atapered waveguide for the purpose of explaining the broadband propertiesof antennas built in accordance with this invention. It is commonknowledge among those familiar with the properties of electromagneticwaves, that a common rectangular waveguide mode propagates freely inwaveguidesin which the major dimension is greater than one-halfwavelength but is cut off or strongly attenuated in waveguides which aresmaller than this. This attenuation increases as the waveguide becomesprogressively smaller than one-half wavelength.

4 In view of this fact it is evident that a wave having a wavelengthwill propagate freely to the right of the crosssectional area designatedby the letters a, b, c, d, where Moreover, all frequencies higher thanthis will propagate freely and it may be said that when suitably excitedthe waveguide is infinitely broadband at frequencies above the frequencyA ab. However, if the same range of frequencies is transmitted fromcross section a'b'cd', those frequencies having wavelengths greater thanZa'b will be quite strongly attenuated. Because the attenuation isreactive it can be compensated for, and essentially perfect transmissioncan be achieved by means of suitable tuning adjustments in the excitingstructure. However, good transmission is attained at only a small rangeof frequencies, so that the structure is narrow band.

If the exciting structure is moved still further to the left tocross-sectional area a"b"c"d and the attempt is made to transmitfrequencies whose wavelengths are the same as previously, the length ofcut-off waveguide, through which these waves must pass, is greater andthe attenuation, at least in the section from ab"cd" to a'bcd is evenmore severe. Again, transmission at a limited range of frequencies canbe attained by tuning the exciting structure, but the availablebandwidth is even narrower.

From the foregoing, it is evident that if we are faced with the problemof transmitting waves to the right in the Waveguide but restricted tothat part of the guide to the left of section abcd in which to place ourexciting structure, both bandwidth and efliciency will be greatest if weapply our excitation as far to the right in the guide as possible.Improved efficiency as Well as bandwidth results from the fact thatenergy transmitted through a waveguide below cut-oft" is accompanied byvery large currents in the waveguide walls, resulting in excessiveresistive power loss. The further below cut-off in the guide, thegreater are the wall currents and the higher the loss.

To those acquainted with the principles of electromagnetic theory, theconcept of free space as a sharply tapered waveguide is readilycomprehensible. Wave modes closely analogous to the wave modes in thewaveguide exist in free space. The free space waveguide might be said totaper out from the point where the transmitting voltage is applied witha solid angle of taper equal to 21r steradians, beyond the radius andhemispherical crosssection related to the wavelength in a manner notidentical but closely analogous to the manner in which cross-section abis related to the wavelength, the waves propagate freely. At smallerradii, corresponding to sections ab' and a"b in the waveguide the wavesdo not propagate freely and can be transmitted effectively only by theuse of auxiliary tuning. As in the case of the waveguide, bandwidth andefiiciency are both maximized if the excitation is applied as close aspossible to the cross-section corresponding to section ab in FIGURE 8 atwhich the waves begin to propagate freely. In terms of LF antennas, thismeans applying the excitation at maximum radius.

It is evident from the foregoing description that the present inventionaccomplishes exactly this, since by means of the circular grounddistribution bus and ground ring, together with the loop inductancesformed by the guy wires, the exciting currents and voltages are appliedat the perimeter of the antenna (corresponding to crosssection a'b'c'd'in the tapered waveguide) rather than at the base of the tower(corresponding to cross-section a"b"cd"). In the ground area between thetower base and the antenna perimeter, which corresponds to the sectionof waveguide wall between sections a"b"c"d" and ab'c'd', current flowand attendant ground losses are drastically reduced.

FIGURE 9 shows another arrangement for reducing ground current losseswhile keeping the cost of the antenna installation down. The antenna,with which the ground current distribution structure shown in FIGURE 9is used, is the same as that shown in FIGURE 4. To preserve simplicityin drawing and explanation, only so much of the antenna structure ofFIGURE 4 is shown as to enable one to easily see the connections of theantenna structure to the ground current distributing structure.

Instead of using a bus ring 46 and equalizing reactances 54 as shown inFIGURE 4 to obtain current distribution and to reduce ground currentdensity, a ground conductor ring is used consisting of multipleinsulated conductors illustrated by the three conductors 80, 82, 84,respectively, which are buried in the ground. These conductors eachincludes a central conductor respectively C, 82C, 84C, surrounded bydielectric material respectively 80D, 82D, 84D. The conductors formthree concentric rings, and are placed in the ground substantially inthe same horizontal plane. The ring is placed in the ground about at thesame position with respect to the antenna tower as the position of thebus ring 46, that is just inside the circle defined by the anchoredupper guy wires.

As shown in the drawing, the transmitter 58 has the terminal previouslyconnected to the distributor ring 46, connected to the conductors 80C,82C, 84C. The dielectric insulating material 80D, 82D, and 84D, betweenthe respective inner conductors and ground acts as the dielectric forcapacitors with the inner conductors and ground as the capacitiveplates. The capacitance thus established distributes the current intothe ground equally all around the large circle at the periphery of theantenna whereby the ground current density is minimized, as wasdescribed in connection with FIGURE 3. Since the conductors 80C, 82C,84C, replace the current distribution bus 46, and the capacitancebetween the conductor, which is insulated, and the surrounding earth,replace the equalizing reactances 54, both of these are eliminated.Thus, effectively, instead of inductors coupling a distributing bus toground, the c oupling is made capacitive by this embodiment of theinvention.

While the description herein refers to radiating conductors supported bya single tower and thereby describing a cone, the invention is not to beconstrued as being limited thereby since it is evident to those skilledin the art that other means or arrangements of support might be used.For example, multiple towers at the corners of a regular polygon mightbe used to support radiating conductors thereby describing a surfacewhich resembles a conic frustum. Alternatively, the conductors might besupported from a rubber or plastic membrane inflated to form ahemisphere.

There has accordingly been described a novel, useful, antenna of themonopole type which has a construction and excitation such that thecurrent concentration losses in the ground are minimized while the costof construction of the antenna is minimized. In addition, the bandwidthof the antenna is improved by the use of the guy wires as radiatingloops along with the usual radiating conductors.

I claim:

11. In a monopole antenna of the type having a plurality of radiatorssaid radiators having one end connected to the top of a tower andextending outwardly therefrom and each of the other ends being supportedfrom the ground at a distance from said tower by means of a straininsulator and a support cable, the improvement comprising a groundedclosed loop conductor, means for connecting each of said support cablesat spaced points around said conductor to be grounded thereby, means forexciting said plurality of radiators and means coupling said groundedloop conductor to said means for exciting said plurality of radiatorsfor obtaining a ground current distribution pattern which emanates from.said ground loop conductor instead of from the base of said tower.

2. In a monopole antenna of the type wherein the antenna radiators aresupported from a tower which is maintained vertical by means of aplurality of guy wires connected thereto, the improvement comprisingmeans connecting said guy wires to form an inductance winding, meansconnecting one end of said inductance winding to said radiators, andmeans for applying excitation to the other end of said inductancewinding.

3. A monopole antenna comprising a plurality of radiating wires, meansfor supporting said plurality of radiating wires above the earth todescribe the surface of a cone with its apex pointed away from theearth, said supporting means including a plurality of guy wires, meansfor connecting said plurality of :guy wires in the form of an inductancewinding, means connecting one end of the inductance winding formed bysaid plurality of guy wires to one end of each one of the radiatingwires, and means for applying excitation to the other end of saidinductance winding formed by said guy wires.

4. A monopole antenna comprising a plurality of radiating wires, meansfor supporting said plurality of radiating wires above the earth todescribe the surface of a cone with its apex pointed away from theearth, said supporting means including a plurality of guy wires, meansfor connecting said plurality of guy wires in the form of an inductancewinding, means connecting one end of the inductance winding formed bysaid plurality of guy wires to one end of all of the radiating wires,means for applying excitation to the other end of said inductancewinding formed by said guy wires, and means conductively coupled to saidmeans for exciting said plurality of radiating conductors andinsulatingly coupled to all of said radiating conductors for securing aground current distribution pattern which emanates from the periphery ofsaid cone on the surface of the earth.

5. A monopole antenna as recited in claim 4 wherein said meansconductively coupled to said means for exciting said plurality ofradiating conductors and insulatingly coupled to all of said radiatingconductors for securing a ground current distribution pattern comprisesan insulated conductor ring buried in the earth at substantially thelocation of the base of said cone, said insulated conductor ringcomprising a central conductor and a dielectric sheath, said means forexciting said plurality of radiating conductors being connected to saidcentral conductor.

6. An antenna .as recited in claim 4 wherein said means for securing aground current pattern which emanates from the periphery of said conecomprises a closed loop conductor buried in the earth and substantiallyconforming to the periphery of said cone, a current distribution bus,means connecting each one of said radiating wires insulatingly to saidcurrent distribution bus, means connecting said exciting means to saidcurrent distribution bus, and a plurality of reactance means a differentone of which is connected between the point to which a different one ofsaid radiating conductors is insulatingly connected on said currentdistribution bus and an adjacent point on said closed loop conductorburied in said ground.

7. The improvement in an umbrella antenna of the type having a pluralityof radiators having one end supported from the top of a tower, each ofsaid radiators extending outwardly from said tower and having its otherend connected to a strain insulator and then through a support cable toground, said improvement comprising a plurality of insulated conductorrings buried in'the earth, said insulated conductor rings beingconcentrically disposed with said tower at the axis and being placed atthe periphery of the base of a cone described by said plurality ofradiators and support cables, each said insulated conductor ringincluding a central conductor and a dielectric sheath, a source ofexcitation for said radiators, and means for connecting said sourcebetween said radiators and the central conductors of all of saidconductor rings.

8. The improvement in an umbrella antenna of the type having a pluralityof radiators having one end supported from the top of a tower, each ofsaid radiators extending outwardly from said tower and having its otherend connected to a strain insulator and then through a support cable toground, said improvement comprising a circular ground currentdistribution bus mechanically supported from each one of the supportcables, a source of excitation for said plurality of radiators, meansfor connecting said source between said radiators and said groundcurrent distribution bus, and a plurality of impedance means connectedbetween spaced points around said ground current distribution bus andground, each of said impedance means having its values selected forequalizing the flow of current between said ground current distributionbus and ground.

9. An umbrella type antenna comprising a plurality of radiatingconductors, means for supporting said plurality of radiating conductorsabove the earth in the surface of a cone having its apex pointed awayfrom the earth, said means including a support tower, means for holdingsaid support tower erect including at least one set of upper guy wiresand one set of lower guy wires, said support tower having an upper endmeans at the upper end of said support tower for connecting together anupper end of each one of said radiating wires and one end of a first ofsaid upper guy wires, a separate insulator attached to the other end ofeach of said radiating wires, a separate support cable connected betweeneach one of said insulators and ground, means for insulatinglyconnecting one end of each of said guy wires except said first of saidupper guy wires to said antenna support tower at spaced points betweenits top and bottom, means for insulatingly connecting the other end ofsaid upper set of guy wires to ground at the periphery of said cone,means for insulatingly connecting the other end of said lower set ofsaid guy wires to ground, a first conductor connecting the other end ofsaid first of said upper set of guy wires which is closest to ground toother end of a first of said lower set of guy wires which is closest toground, a second conductor connected between the other end of said firstof said lower set of guy wires and the end of a second of said upper setof guy wires which is closest to said antenna support tower, and meansfor applying excitation to the other end of said second one of saidupper set of guy wires which is closest to ground.

10. An umbrella type antenna comprising a plurality of radiatingconductors, means for supporting said plurality of radiating conductorsabove the earth in the surface of a cone having its apex pointed awayfrom the earth, said means including a support tower, means for holdingsaid support tower erect including at least one set of upper guy wiresand lower guy wires, said support tower having an upper end, means atthe upper end of said support tower for connecting together an upper endof all of said radiating wires and one end of a first of said upper guywires, a separate insulator attached to the other end of each of saidradiating wires, a separate support cable connected between each one ofsaid insulators and ground, means for insulatingly connecting each ofsaid guy Wires except said first of said guy wires to said antenna atspaced points between its top and bottom, means for insulatinglyconnecting said upper set of guy wires to ground at the periphery ofsaid cone, means for insulatingly connecting the lower set of said guywires to ground, a first conductor connecting the end of said first ofsaid upper set of guy wires which is closest to ground to the end of afirst of said lower set of guy wires which is closest to ground, asecond conductor connected between the other end of said first of saidlower set of guy wires and the end of a second of said upper set of guywires which is closeset to said antenna, means for applying excitationto the end of said second one of said upper set of guy wires which isclosest to ground, and means connected to said antenna for securing aground current distribution which emanates from the periphery of saidcone at the surface of the earth, said means including a ground currentdistribution bus in the form of a closed loop conductor connected toeach one of said support cables substantially at the periphery of saidcone, means connecting said means for applying excitation to said groundcurrent distribution bus, a second conductor in the form of a closedloop which is buried in the ground at the periphery of said cone, and aplurality of reactance means a different one of which couples saidcurrent distribution bus to said closed loop conductor buried in saidearth at the location at which attachment is made to said supportcables.

11. An antenna as recited in claim 10 wherein there are a plurality ofupper and lower sets of guy wires, said plurality of upper and lowersets of guy wires being spaced around said antenna tower for maintainingit erect, means for connecting one end of a first guy wire in each ofsaid upper sets to said means at the top of said antenna tower forinterconnecting with said ends of said radiating wires, means forinsulatingly connecting one end of all of said guy wires in said upperand lower sets except said first guy wires to said support tower, meansfor insulatingly connecting the other end of all said guy wires in saidupper and lower sets to ground, a first connecting conductor for eachupper and lower set of guy wires for connecting the lower end of eachsaid first guy wire in each said upper set to the lower end of a firstguy wire in each said lower set, a second connecting conductor connectedbetween the upper end of each said first guy wire in said lower set andthe upper end of a second guy wire in each said upper set, and means forconnecting the lower end of each said second guy wire in said upper setto said current distribution bus.

12. An umbrella ty-pe antenna comprising a plurality of radiatingconductors, means for supporting said plurality of radiating conductorsabove the earth in the surface of a cone having its apex pointed awayfrom the earth, said means including a support tower, means for holdingsaid support tower erect including at least one set of upper guy wiresand lower guy wires, said support tower having an upper end, means atthe upper end of 40 said support tower for connecting together an upperend of all of said radiating wires and one end of a first of said upperguy wires, a separate insulator attached to the other end of each ofsaid radiating Wires, a separate support cable connected between eachone of said insulators and ground, means for insulatingly connecting oneend of each of said guy wires except said first of said guy wires tosaid support tower at spaced points between its top and bottom, meansfor insulatingly connecting the other ends of each of said upper set ofguy wires to ground at the periphery of said cone, means forinsulatingly connecting the other ends of the set of lower guy wires toground, a first conductor connecting the end of said first of said upperset of guy wires which is closest to ground to the end of a first ofsaid lower set of guy wires which is closest to ground, a secondconductor connected between the other end of said first of said lowerset of guy wires and the end of a second of said upper set of guy wireswhich is closest to said antenna, means for applying excitation to theend of said second one of said upper set of guy wires which is closestto ground, and means connected to said antenna for securing a groundcurrent distribution which emanates from the periphery of said cone atthe surface of the earth including a plurality of conductor rings beingconcentrically disposed with said tower at the axis and being at theperiphery of the base of said cone, each said conductor ring including acentral conductor and a dielectric sheath, and means connecting saidmeans for applying excitation to the central conductors of saidconductor rings.

References Cited by the Examiner UNITED STATES PATENTS 768,005 8/1904Stone 343-890 945,475 1/1910 Pfund 343-849 958,209 5/1910 Arco 343-8471,214,591 2/1917 Reuthe 343-847 1,595,166 8/1926 Scheller 343-8452,263,460 11/1941 Gerth et a1, 343-875 2,473,377 6/1949 Koch 343-8492,527,609 10/1950 Willoughby 343-860 2,746,040 5/1956 Martin 343-8462,998,604 8/1961 Seeley 343-874 FOREIGN PATENTS 299,766 12/ 1920Germany. 176,803 7/1923 Great Britain.

HERMAN KARL SAALBACH, Primary Examiner.

45 W. K. TAYLOR, P. L. GENSLER, Assistant Examiners.

1. IN A MONOPOLE ANTENNA OF THE TYPE HAVING A PLURALITY OF RADIATORSSAID RADIATORS HAVING ONE END CONNECTED TO THE TOP OF A TOWER ANDEXTENDING OUTWARDLY THEREFROM AND EACH OF THE OTHER ENDS BEING SUPPORTEDFROM THE GROUND AT A DISTANCE FROM SAID TOWER BY MEANS OF A STRAININSULATOR AND A SUPPORT CABLE, THE IMPROVEMENT COMPRISING A GROUNDCLOSED LOOP CONDUCTOR, MEANS FOR CNNECTING EACH OF SAID SUPPORT CABLESAT SPACED POINTS AROUND SAID CONDUCTOR TO BE GROUNDED THEREBY, MEANS FOREXCITING SAID PLURALITY OF RADIATORS AND MEANS COUPLING SAID GROUNDEDLOOP CONDUCTOR TO SAID MEANS FOR EXCITING SAID PLURALITY OF RADIATORSFOR OBTAINING A GROUND CURRENT DISTRIBUTION PATTERN WHICH EMANATES FROMSAID GROUND LOOP CONDUCTOR INSTEAD OF FROM THE BASE OF SAID TOWER.